Is jamband music back in style? Did it ever go out of style? Was it ever in style?
An emphasis on live performance, changing up the setlists, extended improvisation that leave the song structure behind, well chosen covers but also a healthy dose of originals, investing in an impressive light show, a relentless touring schedule, and long two-set performances. Is that what we want nowadays?
Twenty-five years ago I was already seeing bands such as Leftover Salmon, moe., String Cheese Incident, Dark Star Orchestra, Strangefolk, Keller Williams, Sector 9, and Yonder Mountain String Band on a regular basis. (Well, 1999 for Yonder and STS9; some of those others date back to as early as '95). I never stopped listening to or going to see Phish, but for the rest of these it's been a long almost twenty year sabbatical.
Now I feel like seeing most, if not all of those bands again, even Widespread Panic who never really grabbed me back in the mid-90's but now I can appreciate. And hey look there's Goose and right behind them heeeeeeeeere's Eggy. So it's not just nostalgia. Now it's now again.